U.S. patent number 5,021,283 [Application Number 07/379,736] was granted by the patent office on 1991-06-04 for woven fabric having multi-layer structure and composite material comprising the woven fabric.
This patent grant is currently assigned to Asahi Kasei Kogyo Kabushiki Kaisha. Invention is credited to Eiji Sato, Koji Takenaka.
United States Patent |
5,021,283 |
Takenaka , et al. |
June 4, 1991 |
Woven fabric having multi-layer structure and composite material
comprising the woven fabric
Abstract
Disclosed is a woven fabric having a plurality of fabric layers
which are integrated through combined portions formed by
interlacing warps or wefts of one of adjacent layers of some of
warps or wefts of said one layer and warps or wefts of the other
layer or some of warps or wefts of said other layer with common
wefts or warps, wherein a set of adjacent four layers comprises
recurring structural units comprising (A) a part having one
combined portion formed by intermediate two layers, (B) a first
non-combined part having no combined portion, (C) a part having two
combined portions formed by subsequent two layers, respectively,
and (B) a second non-combined part having no combined portion. A
honeycomb structure having cells of a shape of tetragons, hexagons
or a combination thereof is formed among the entire layers when the
multi-layer fabric is expanded. 40-100 wt. % of the fibers
constituting the fabric are organic fibers which are infusible or
have a melting point of at least 300.degree. C. and have an initial
modulus of at least 250 g/d, and 0-60 wt. % of the fibers
constituting the fabric are inorganic fibers or metal fibers. A
composite material comprising the multi-layer fabric as a
reinforcer and a thermoplastic resin as a matrix has good
mechanical strengths and thermal resistance and is valuable, e.g.,
as a structural material for an aircraft.
Inventors: |
Takenaka; Koji (Ishikawa,
JP), Sato; Eiji (Nobeoka, JP) |
Assignee: |
Asahi Kasei Kogyo Kabushiki
Kaisha (Osaka, JP)
|
Family
ID: |
27302137 |
Appl.
No.: |
07/379,736 |
Filed: |
July 13, 1989 |
Foreign Application Priority Data
|
|
|
|
|
Mar 31, 1987 [JP] |
|
|
62-76364 |
Mar 31, 1987 [JP] |
|
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62-76365 |
Dec 19, 1987 [JP] |
|
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62-320153 |
|
Current U.S.
Class: |
428/116;
139/384R; 139/390; 139/420A; 244/133; 244/2; 428/118; 428/902 |
Current CPC
Class: |
D03D
11/02 (20130101); Y10S 428/902 (20130101); Y10T
428/24165 (20150115); Y10T 428/24149 (20150115) |
Current International
Class: |
D03D
11/00 (20060101); B32B 003/12 (); D03D 001/00 ();
D03D 011/02 (); D03D 015/00 () |
Field of
Search: |
;139/384R,390,42A
;244/2,133 ;428/116,118,252,902 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Cannon; James C.
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner
Parent Case Text
This application is a continuation of application Ser. No.
07/174,858, filed Mar. 29, 1988 now abandoned.
Claims
We claim:
1. A woven fabric having a multi-layer structure, which comprises a
plurality of woven fabric layers which are integrated through
combined portions formed by interlacing warps or wefts of one of
adjacent woven fabric layers or some of warps or wefts of said one
woven fabric layer and warps or wefts of another woven fabric layer
or some of warps or wefts of said other woven fabric layer with
common wefts or warps, wherein a set of adjacent four woven fabric
layers comprises recurring structural units comprising (A) a part
having one combined portion formed by intermediate two woven fabric
layers, (B) a first non-combined part having no combined portion,
(C) a part having two combined portions each formed by adjacent two
woven fabric layers, respectively, and (B) a second non-combined
part having no combined portion; a honeycomb structure having a
plurality of cells having a shape of tetragons, hexagons or a
combination of tetragons and hexagons is formed among the entire
woven fabric layers when the multi-layer woven fabric is expanded
in the thickness direction; and 40 to 100% by weight of the fibers
constituting the woven fabric are one or more kinds of organic
fibers selected from the group consisting of aromatic polyamide
fibers, polybenzoxazole fibers and polybenzothiazole fibers, which
have a tensile strength of at least 18 g/d and an initial modulus
of at least 300 g/d, and 0 to 60% by weight of the fibers
constituting the woven fabric are carbon fibers wherein the ratio
of the density of the expanded multi-layer woven fabric to the
density of the multi-layer woven fabric before the expansion is in
the range of from 0.05 to 0.3, the density of the expanded
multi-layer woven fabric being an apparent density determined from
the volume and weight measured when the multi-layer woven fabric is
normally expanded so that the inner angles of each tetragonal or
hexagonal cell are equal; and the sum of the cover factor kw in the
warp direction and the cover factor kf in the weft direction, which
are represented by the following formulas, is at least 300 and the
sum of the cover factor Kw in the warp direction and the cover
factor Kf in the weft direction, which are represented by the
following formulas, is at least 3,000: ##EQU2## wherein kw and kf
stand for cover factors of each layer constituting the multi-layer
woven fabric in the warp direction and weft direction,
respectively, Kw and Kf stand for cover factors of the entire
multi-layer woven fabric in the warp direction and weft direction,
respectively; dw and df stand for warp and weft densities of each
layer, expressed by the number of warps or wefts per inch
respectively; Dw and Df stand for total warp and weft densities of
the entire multi-layer woven fabric, expressed by the number of
warps or wefts per inch, respectively; d stands for the fineness
(denier) of warps or wefts; and .rho. stands for the density
(g/cm.sup.3) of the fibers.
2. A woven fabric having a multi-layer structure according to claim
1, wherein the warps constituting the woven fabric are composed of
fibers selected from the group consisting of aromatic polyamide
fibers, polybenzoxazole fibers and polybenzothiazole fibers, which
have a tensile strength of at least 18 g/d and an initial modulus
of at least 300 g/d.
3. A woven fabric having a multi-layer structure according to claim
1, wherein the wefts are composed of carbon fibers or glass
fibers.
4. A composite material having a honeycomb structure, which
comprises as a matrix a thermoplastic resin having a heat
distortion temperature of at least 150.degree. C. and as a
reinforcer an expanded woven fabric having a multi-layer structure,
the amount of fibers constituting the multi-layer woven fabric
being 20 to 70% by weight and the amount of the resin constituting
the matrix being 80 to 30% by weight, based on the weight of the
composite material, said multi-layer woven fabric comprising a
plurality of woven fabric layers which are integrated through
combined portion formed by interlacing warps or wefts of one of
adjacent woven fabric layers or some of warps or wefts of said one
woven fabric layer and warps or wefts of the other woven fabric
layer or some of warps or wefts of said other woven fabric layer
with common wefts or warps, wherein a set of adjacent four woven
fabric layers comprises recurring structural unit comprising (A) a
part having one combined portion formed by intermediate two woven
fabric layers, (B) a first non-combined part having no combined
portion, (C) a part having two combined portions each formed by
adjacent two woven fabric layers, respectively, and (B) a second
non-combined part having no combined portion; a honeycomb shape of
tetragons, hexagons or a combination of tetragons and hexagons is
formed among the entire woven fabric layers when the multi-layer
woven fabric is expanded in the thickness direction; 40 to 100% by
weight of the fibers constituting the woven fabric are one or more
kinds of organic fibers selected from the group consisting of
aromatic polyamide fibers, polybenzoxazole fibers and
polybenzothiazole fibers, which have a tensile strength of at least
300 g/d, and 0 to 60% by weight of the fibers constituting the
woven fabric are inorganic fibers or metal fibers wherein the ratio
of the density of the expanded multi-layer woven fabric to the
density of the multi-layer woven fabric before the expansion is in
the range of from 0.05 to 0.3, the density of the expanded
multi-layer woven fabric being an apparent density determined from
the volume and weight measured when the multi-layer woven fabric is
normally expanded so that the inner angles of each tetragonal or
hexagonal cell are equal; and the sum of the cover factor kw in the
warp direction and the cover factor kf in the weft direction, which
are represented by the following formulas, is at least 300 and the
sum of the cover factor kw in the warp direction and the cover
factor Kf in the weft direction, which are represented by the
following formulas, is at least 3,000: ##EQU3## wherein kw and kf
stand for cover factors of each layer constituting the multi-layer
woven fabric in the warp direction and weft direction,
respectively, Kw and Kf stand for cover factor of the entire
multi-layer woven fabric in the warp direction and weft direction,
respectively; dw and df stand for warp and weft densities of each
layer, expressed by the number of warps or wefts per inch
respectively; Dw and Df stand for total warp and weft densities of
the entire multi-layer woven fabric, expressed by the number of
warps or wefts per inch, respectively; d stands for the fineness
(denier) of warps or wefts; and .rho. stands for the density
(g/cm.sup.3) of the fibers.
5. A composite material according to claim 4, wherein the resin
constituting the matrix is at least one polymer selected from the
group consisting of:
a) aromatic polyamide-imides represented by the following general
formula: ##STR6## b) aromatic polyether-imides represented by the
following general formula: ##STR7## c) aromatic polyesters
represented by the following general formula: ##STR8## d)
polyether-sulfones represented by the following general
formula:
3) polyether-ether-ketones represented by the following general
formula: ##STR9## f) poly-p-phenylene sulfides represented by the
following general formula:
and g) poly-p-phenylene oxides represented by the following general
formula:
and in the foregoing general formulae a) through g), Ar.sub.1,
Ar.sub.2 and Ar.sub.3, which may be the same or different, stand
for a substituted or unsubstituted divalent aromatic residue
represented by ##STR10## in which X is --O--, --SO.sub.2 --,
--CH.sub.2 -- or --C(CH.sub.3).sub.2 --.
6. A composite material according to claim 4, wherein the apparent
density of the composite material is 0.03 to 0.2 g/cm.sup.3.
7. A composite material according to claim 4, wherein the warps
constituting the multi-layer woven fabric are composed of fibers
selected from the group consisting of aromatic polyamide fibers,
polybenzoxazole fibers and polybenzothiazole fibers, which have a
tensile strength of at least 18 g/d and an initial modulus of at
least 300 g/d, the wefts constituting the multi-layer woven fabric
are composed of carbon fibers and the matrix resin is at least one
member selected from the group consisting of d) the
polyether-sulfones, e) the polyether-ether-ketones and b) the
polyether-imides.
Description
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a multi-layer woven fabric
comprising a plurality of woven fabric layers and having a
three-dimensional structure suitable as a reinforcing fiber for a
fiber-reinforced composite material, and to a composite material
comprising the multi-layer woven fabric as a reinforcer.
More specifically, the present invention relates to a multi-layer
woven fabric in which honeycomb-like cells can be formed by a
specific combination of combined portions and non-combined portions
when the woven fabric is expanded, i.e., opened out, and to a
high-grade composite material having excellent mechanical
characteristics, which is obtained by combining this multi-layer
woven fabric with a specific resin.
(2) Description of the Related Art
As one conventional composite material, there is known a structural
material formed by bonding a surface member forming a surface layer
to a core material having honeycomb-like structure (hereinafter
referred to as "honeycomb core").
In general, conventional honeycomb cores are obtained by coating an
adhesive in stripes spaced equidistantly on a thin sheet such as a
paper, an aluminum foil or a film, laminating and bonding such
adhesive-coated thin sheets, and expanding the bonded structure to
form honeycomb-like structure having a multiplicity of cells.
It is known that a plane woven fabric composed of glass fibers or
the like is used as the sheet material for forming a honeycomb core
according to the abovementioned process, and it is also known that
a composite material is prepared by impregnating this honeycomb
core with a thermosetting resin such as an epoxy resin. However,
this honeycomb core does not have a sufficient tensile strength,
peel strength and shear strength of the bonded surfaces. Although
the use of a honeycomb structural material as a structural material
of an aircraft is now desired, a satisfactory honeycomb structure
has not been obtained because of the abovementioned defect.
U.S. Pat. No. 3,102,559 discloses a composite material formed by
impregnating a honeycomb structure woven from yarns composed of
natural fibers, nylon fibers, glass fibers or the like with a
thermosetting resin. In this composite material, the tensile
strength of the bonded surfaces is improved and a relatively high
compression strength is attained because the weaving honeycomb
structure is combined with the thermosetting resin. However, this
composite material is still unsatisfactory as a structural material
for an aircraft, and since the composite material is brittle, if
the stress is imposed repeatedly, the composite material is liable
to be broken.
Furthermore, a composite material is known which comprises a mat of
carbon fibers or aramid fibers impregnated with a thermosetting
resin. Although this composite has a high tensile strength and an
excellent compression strength, the composite material is brittle
and still has an insufficient impact strength. Accordingly,
application of the composite material to fields where the
conditions are more severe than in the conventional fields, for
example, application to the field of aircraft, is difficult, and
the application range of the composite material is limited. A light
weight is an important condition for application to the field of
aircraft. In this composite material, if it is intended to decrease
the weight, the tensile strength and compression strength must be
reduced, and when stress is imposed repeatedly, the composite
material is liable to be broken and the impact resistance degraded.
Moreover, the composite material exhibits a poor durability and
heat resistance, when an aircraft part is repeatedly exposed to a
high temperature and a low temperature.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a woven
fabric especially suitable for the production of a composite
material which has a light weight, shows an excellent compression
strength in a broad temperature range, is not broken when stress is
imposed repeatedly, and has an excellent impact resistance, and
further, to provide a composite material in which the
above-mentioned properties are most effectively exerted, by using
this woven fabric.
More specifically, in accordance with one aspect of the present
invention, there is provided a woven fabric having a multi-layer
structure, which comprises a plurality of woven fabric layers which
are integrated through combined portions formed by interlacing
warps or wefts of one of adjacent woven fabric layers or some of
warps or wefts of said one woven fabric layer and warps or wefts of
the other woven fabric layer or some of warps or wefts of said
other woven fabric layer with common wefts or warps, wherein a set
of adjacent four woven fabric layers comprises recurring structural
units comprising (A) a part having one combined portion formed by
intermediate two woven fabric layers, (B) a first non-combined part
having no combined portion, (C) a part having two combined portions
each formed by adjacent two woven fabric layers, respectively, and
(B) a second non-combined part having no combined portion; a
honeycomb structure having a plurality of cells having a shape of
tetragons, hexagons or a combination of tetragons and hexagons is
formed among the entire woven fabric layers when the multi-layer
woven fabric is expanded in the thickness direction; and 40 to 100%
by weight of the fibers constituting the woven fabric are organic
fibers which are infusible or have a melting point of at least
300.degree. C. and have an initial modulus of at least 250 g/d, and
0 to 60% by weight of the fibers constituting the woven fabric are
inorganic fibers or metal fibers.
In accordance with another aspect of the present invention, there
is provided a composite material having a honeycomb structure,
which comprises as a matrix a thermoplastic resin having a heat
distortion temperature of at least 150.degree. C. and as a
reinforcer the above-mentioned woven fabric having a multi-layer
structure, the amount of fibers constituting the multi-layer woven
fabric being 20 to 70% by weight and the amount of the resin
constituting the matrix being 80 to 30% by weight.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram illustrating the sectional texture of a
four-layer woven fabric according to the present invention;
FIG. 2 is a diagram showing the shape of cells formed when the
four-layer woven fabric shown in FIG. 1 is expanded;
FIG. 3 is a diagram illustrating the sectional texture of another
four-layer woven fabric according to the present invention;
FIG. 4 is a diagram illustrating the shape of cells formed when the
multi-layer woven fabric shown in FIG. 3 is expanded; and
FIG. 5 is a diagram illustrating the sectional texture of still
another four-layer woven fabric according to the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The multi-layer woven fabric of the present invention comprises a
plurality of woven fabric layers which are integrated through
combined portions formed by interlacing warps or wefts of one of
adjacent woven fabric layers or some of warps or wefts of said one
woven fabric layer and warps or wefts of the other woven fabric
layer or some of warps or wefts of said other woven fabric layer
with common wefts or warps.
In the combined portion, all or some of warps of a two-layer woven
fabric composed of a set of adjacent and confronting upper and
lower yarns are interlaced as the upper or lower warps constituting
the combined portion with one common weft inserted separately from
the two-layer woven fabric, whereby one combined weave structure is
formed.
In the multi-layer woven fabric of the present invention, a set of
adjacent four layers comprises recurring structural units
comprising (A) a part having one combined portion formed by
intermediate two woven fabric layers, (B) a first non-combined part
having no combined portion, (C) a part having two combined portions
each formed by adjacent two woven fabric layers, respectively, and
(B) a second non-combined part having no combined portion, and a
honeycomb structure is formed among the entire woven fabric layers
when the multi-layer woven fabric is expanded (i.e., opened) in the
thickness direction.
By formation of the honeycomb structure among the entire woven
fabric layers, a weight-decreasing effect is attained in a
composite material prepared from this multi-layer woven fabric, and
in turn, a high specific strength is realized in the composite
material.
In the multi-layer woven fabric of the present invention,
preferably the ratio of the density of the expanded multi-layer
woven fabric to the density of the multi-layer woven fabric before
the expansion is in the range of from 0.05 to 0.3, wherein the
density of the expanded multi-layer woven fabric means an apparent
density determined from the volume and weight measured when the
multi-layer woven fabric is normally expanded so that the inner
angles of respective tetragonal and/or hexagonal cells are
equal.
The density varies according to the size of cells formed by the
expansion, though the density is influenced to some extent by the
fineness of warps or wefts constituting the woven fabric, the weave
density, and the like. A multi-layer woven fabric having a higher
density ratio is preferable as a reinforcer because it imparts a
high mechanical performance, but the multi-layer woven fabric is
disadvantageous from the viewpoint of the weight-decreasing effect.
On the other hand, a multi-layer woven fabric having a low density
ratio is not preferred as a reinforcer because the mechanical
performance is degraded.
In a high-grade composite material intended in the present
invention, such as a structural material for an aircraft, the
intended object cannot be attained only by a light weight or high
mechanical properties, but the weight must be high and the
mechanical performance must be excellent. In the multi-layer woven
fabric of the present invention, to satisfy this requirement,
preferably the above-mentioned density ratio is in the range of
from 0.05 to 0.3.
As pointed out hereinbefore, in the present invention, a honeycomb
structure must be formed among the entire layers of the multi-layer
woven fabric so that the ratio between the densities before and
after the expansion is in a specific range. The structural units
forming this honeycomb structure will now be described in detail
with reference to the accompanying drawings illustrating
embodiments of the present invention.
FIG. 1 is a diagram illustrating the section of a set of four
adjacent layers of the multi-layer woven fabric of the present
invention. Referring to FIG. 1, woven fabric layers 11, 12, 13, and
14 having a plain weave texture have recurring structural units
comprising continuous combined parts A and C for every four
non-combined parts B. In part A, warps of second and third woven
fabric layers 12 and 13 are interlaced with three continuously
inserted combining wefts 30a, 30b, and 30c through plain weave
textures to form a middle combined portion. This combined portion
constitutes an independent single woven fabric layer. Therefore,
part A has a three-layer structure comprising the first woven
fabric layer 11, the middle combined portion layer, and the fourth
woven fabric layer 14. In part C, warps of the first and second
woven fabric layers 11 and 12 are interlaced with three
continuously inserted combining wefts 31a, 31b and 31c through
plain weave textures to form an upper combined portion, and warps
of the third and fourth woven fabric layers 13 and 14 are
interlaced with three continuously inserted combining wefts 32a,
32b, and 32c through plain weave textures to form a lower combined
portion. Therefore, in part C, a two-layer structure is formed
comprising the upper and lower combined portions. If the
multi-layer woven fabric having the above-mentioned structure is
expanded, a three-dimensional woven fabric having a honeycomb
structure as shown in FIG. 2 is formed.
The lengths of the combined portions in parts A and C can be
adjusted by increasing or decreasing the number of combined points
of warps and wefts of the two woven fabric layers participating in
the formation of the combined portions, and therefore, the number
of combined points can be appropriately determined according to the
intended use of the honeycomb structure or the desired honeycomb
cell shape. For example, a honeycomb structure formed of modified
tetragons or a honeycomb structure formed of a combination of
tetragons and hexagons can be obtained by changing the length of
the combined portions in parts A and C.
Referring to FIG. 3 illustrating another embodiment of the
multi-layer woven fabric according to the present invention, each
woven fabric layer has a plain weave texture and interlaminar
combined portions are formed in parts A and C. In part A, warps 12a
and 12b of the second woven fabric layers 12 and warps 13a and 13b
of the third woven fabric layer 13 are interlaced with combining
wefts 30a and 30b to form a middle combined portion. In part C,
warps of the first woven fabric layer 11 and warps of the second
woven fabric layer 12 are interlaced with combining wefts 31a and
31b to form an upper combined portion, and warps of the third woven
fabric layer 13 and warps of the fourth woven fabric layer 14 are
interlaced with combining wefts 32a and 32b to form a lower
combined portion. In parts A and B, each combined portion in each
layer is formed by one-point combination with two combining wefts
for every four plain weave textures. Accordingly, if this
four-layer woven fabric is expanded, a three-dimensional woven
fabric having diamond-shaped cells in the section is formed, as
shown in FIG. 4.
FIG. 5 shows an example of the multi-layer woven fabric in which
some of warps 11a, 12a, 13a, and 14a of respective woven fabric
layers 11 through 14 are interlaced with combining wefts 30a, 31a,
and 32a to form combined parts A and C and non-combined parts
B.
The length of the non-combined part B is not particularly critical.
If the length of the non-combined part B is increased, a woven
fabric having a honeycomb structure having larger polygonal cells
can be obtained, and therefore, a fibrous material suitable for the
production of a composite material satisfying the requirement of
reducing the weight and increasing the size can be provided. In
contrast, if the length of the non-combined part B is shortened, a
multi-layer woven fabric having a dense and strong honeycomb
structure can be provided, which is suitable as an industrial
material.
The texture of each woven fabric layer is not limited to the
above-mentioned plain weave texture, and other textures, for
example, a twill weave texture and a satin weave texture, can be
optionally selected.
In the multi-layer woven fabric of the present invention, at least
four layers of woven fabrics are integrated to form honeycomb-like
structure having cells in the section of the multi-layer woven
fabric. The thickness of the multi-layer woven fabric can be
increased by increasing the number of woven fabric layers to be
superposed.
The multi-layer woven fabric of the present invention can be
coincidently prepared by using a weaving machine having many
shuttles on both sides, for example, a fly weaving machine provided
with a plurality of dobbies or a rapier loom provided with a
plurality of dobbies. Where the number of woven fabric layers to be
superposed is increased, a jacquard opener or a plurality of warp
beams are disposed and a rapier loom provided with a plurality of
openers and a plurality of weft inserting mechanisms is used.
Moreover, a loom provided with a mechanism for intermittently
stopping feeding of warps and winding of a woven fabric
synchronously with the movement of the weave texture is used.
In the present invention, 40 to 100% by weight of the total fibers
constituting the multi-layer woven fabric must be organic fibers
which are infusible or have a melting point of at least 300.degree.
C. and have an initial modulus of at least 250 g/d, and 0 to 60% by
weight of the fibers must be inorganic fibers or metal fibers.
The constitution of the fibers forming the multi-layer woven fabric
of the present invention is very important. The multi-layer woven
fabric of the present invention is characterized in that 40 to 100%
by weight of the total fibers of the multi-layer woven fabric are
organic fibers which are infusible or have a melting point of at
least 300.degree. C. and have an initial modulus of at least 250
g/d.
Where the composite material is used as a structural material of an
aircraft according to the object of the present invention, the
mechanical performance as the structural material must be
maintained in a broad temperature range of from a low temperature
to a high temperature under severe conditions such that the
material is repeatedly exposed to high and low temperatures. Also,
the fibers per se acting as the reinforcer must have a high heat
resistance. From this viewpoint, the fibers must be infusible or
have a melting point of at least 300.degree. C. Moreover, the
fibers must not be broken even if subjected to a heat cycle where
the fibers are exposed to high and low temperatures repeatedly. The
specific organic fibers are advantageous over glass fibers and the
like in that the impact resistance is excellent and the fibers are
rarely broken even under a severe heat cycle.
The organic fibers used in the present invention must have an
initial modulus of at least 250 g/d. Namely, the compression
strength, which is one of the properties required for a honeycomb
composite material, must be high. In the composite material, the
compression stress is mainly applied in the length direction of
warps or wefts constituting the woven fabric as the reinforcer, and
in the case of fibers having a low initial modulus, deformation is
easily caused and a high compression strength cannot be obtained.
This liability to deformation is especially conspicuous at high
temperatures. Accordingly, to obtain a composite material capable
of retaining a high compression strength even at high temperatures,
the initial modulus of organic fibers constituting the woven fabric
must be high. Where the composite material is used as a structural
material of an aircraft or the like according to the object of the
present invention, the initial modulus of the organic fibers must
be at least 250 g/d, preferably at least 300 g/d.
The mixing ratio of the organic fibers to inorganic fibers or metal
fibers is important. If the amount of the organic fibers is smaller
than 40% by weight and the amount of the inorganic fibers or metal
fibers is larger than 60% by weight, although a high heat
resistance is attained, high mechanical properties are difficult to
maintain because of breakage of the fibers (especially, the
inorganic fibers) under the above-mentioned heat cycle or metal
fatigue in the case of the metal fibers. Moreover, since the
inorganic fibers or metal fibers have a poor bendability, a
satisfactory mechanical performance cannot be realized. In the
multi-layer woven fabric of the present invention, it is not always
necessary to use the inorganic fibers or metal fibers, and
according to the object, the organic fibers can be used alone. The
amount of inorganic fibers or metal fibers is optionally within the
range of from 0 to 60% by weight according to the intended use.
As the organic fibers used in the present invention, which are
infusible or have a melting point of at least 300.degree. C., there
can be mentioned, for example, fibers of aromatic polyamides
represented by poly-m-phenylene isophthalamide and poly-p-phenylene
terephthalamide; aromatic polyamide-imides derived from an aromatic
diamine such as p-phenylene diamine or 4,4'-diaminodiphenyl ether
and an aromatic tri- or tetra-basic acid such as trimellitic
anhydride or pyromellitic anhydride; aromatic polyimides; aromatic
polyesters derived from an aromatic dicarboxylic acid or a
derivative thereof and an aromatic diol; polybenzoxazoles such as
polybenzoxazole,
polybenzo[1,2-d;5,4-d']bisoxazol-2,6-diyl-1,4-phenylene
polybenzo[1,2-d;4,5-d']bisoxazol-2,6-diyl-1,4-phenylene,
polybenzo[1,2-d;4,5-d']bisoxazol-2,6-diyl-4,4'-biphenylene and
poly-6,6'-bibenzoxazol-2,2'-diyl-1,4-phenylene; and
polybenzothiazoles such as polybenzothiazole,
polybenzo[1,2-d;5,4-d']bisthiazol-2,6-diyl-1,4-phenylene,
polybenzo[1,2-d;4,5-d']bisthiazol-2,6-diyl-4,4'-biphenylene and
poly-6,6'-bibenzothiazol-2,2'-diyl-1,4-phenylene. Of these organic
fibers, fibers of para-oriented aromatic polyamides such as
poly-p-phenylene terephthalamide and poly(p-phenylene-3,4-diphenyl
ether) terephthalamide, and fibers of poly-benzoxazoles or
polybenzothiazoles are especially preferably used as the organic
fibers in the present invention because high-tenacity fibers having
a tensile strength of at least 18 g/d and an initial modulus of at
least 300 g/d can be obtained.
As specific examples of the inorganic or metal fibers, there can be
mentioned carbon fibers obtained from polyacrylonitrile fibers,
pitch type carbon fibers obtained from pitch, glass fibers such as
fibers of E glass, S glass and C glass, alumina fibers, silicon
carbide fibers, and fibers of silicon nitride and boron nitride. Of
these fibers, carbon fibers and glass fibers are preferably used in
the present invention because of a good handling property and from
the economical viewpoint.
These fibers are ordinarily used in the form of multi-filament
yarns as warps or wefts, and the intended object of the present
invention can be attained even if the fibers are used in the form
of spun yarns.
In connection with the thickness, that is, the fineness of the
fibers of the present invention, preferably the single filament
fineness is 0.1 to 50 d and the fineness of multi-filament yarns
used as warps and wefts is 50 to 6,000 d, although these values not
particularly critical.
The above-mentioned organic fibers and inorganic or metal fibers
can be used as either warps or wefts for the production of the
multi-layer woven fabric. Both kinds of fibers may be mix-woven, or
one kind of fibers may be used as warps and the other kind of
fibers may be used as wefts, according to need. Since inorganic
fibers or metal fibers have a poor bending resistance and
bendability, it is especially preferable that the organic fibers
are used for warps and the inorganic or metal fibers are used for
wefts. Of course, the organic fibers also can be used for wefts. In
accordance with one preferred embodiment of the present invention,
aromatic polyamide fibers, polybenzoxazole fibers or
polybenzothiazole fibers having a tensile strength of at least 18
g/d and an initial modulus of at least 300 g/d are used for warps
and carbon fibers or glass fibers are used for wefts.
In the multi-layer woven fabric of the present invention, the cover
factors of warps and wefts constituting the woven fabric are
represented by the following formulas, and preferably the sum of
the cover factor kw in the warp direction and the cover factor kf
in the weft direction is at least 300 and the sum of Kw and Kf
defined below is at least 3,000: ##EQU1## wherein kw and kf stand
for cover factors of each layer constituting the multi-layer woven
fabric in the warp direction and weft direction, respectively, Kw
and Kf stand for cover factors of the entire multi-layer woven
fabric in the warp direction and weft direction, respectively; dw
and df stand for warp and weft densities of each layer expressed by
the number of warps or wefts per inch, respectively; Dw and Df
stand for total warp and weft densities of the entire multi-layer
textile fabric, expressed by the number of warps or wefts per inch,
respectively; d stands for the fineness (denier) of warps or wefts;
and .rho. stands for the density (g/cm.sup.3) of the fibers.
There is no established theory concerning the weaving limit by the
cover factor. In the multi-layer woven fabric of the present
invention, the cover factor is expressed by [cover factor of one
layer x number of layers]. If the cover factor of one layer is
small, the texture strength is reduced. Furthermore, even when the
cover factor of one layer is large, if the cover factor of the
multi-layer woven fabric as a whole is small, the strength of the
formed composite material is degraded. In view of the foregoing, in
the present invention, preferably the sum of kw and kf as the cover
factor is at least 300, especially 300 to 5,000, and the sum of Kw
and Kf is at least 3,000, especially 3,000 to 50,000, particularly
especially 5,000 to 20,000.
The composite material of the present invention is a composite
material consisting essentially of the above-mentioned multi-layer
woven fabric of the present invention and a thermoplastic resin
having a heat distortion temperature of at least 150.degree. C.
In the present invention, the matrix resin must be a thermoplastic
resin. Namely, as pointed out hereinbefore, a composite material
used as a structural material for an aircraft or the like is
repeatedly exposed to low and high temperatures and is used under
severe conditions such that stress is repeatedly imposed under this
heat cycle. The thermosetting resin customarily used as the matrix
resin of the composite material is very brittle, and if the
thermosetting resin undergoes a repeated imposition of the stress
under the repeated heat cycle of low and high temperatures, the
thermosetting resin is very liable to be broken. In contrast, in
the composite material of the present invention, since a specific
thermoplastic resin is used as the matrix resin, the brittleness of
the resin per se is low, and even if the composite material
undergoes a repeated imposition of stress under a repeated heat
cycle of low and high temperatures, few cracks are formed in the
resin, with the result that the structural material is not broken
and the impact resistance is improved.
Since a specific thermoplastic resin is used as the matrix resin,
the resin is deformed in follow-up with the deformation of
reinforcing fibers constituting the multi-layer woven fabric and
the performances of the reinforcing fibers can be completely
utilized. Therefore, mechanical strength characteristics such as
breaking strength and tensile strength are increased and a very
high reinforcing effect can be attained.
In view of the foregoing, the rigidity of the thermoplastic resin
used in the present invention is ordinarily determined according to
the deformability of the reinforcing fibers used. Namely, in the
present invention, preferably a thermoplastic resin having an
elongation equal to or higher than the elongation of the
reinforcing fibers is used.
In the composite material of the present invention, the heat
distortion temperature of the matrix resin must be at least
150.degree. C. In order to obtain a composite material capable of
exerting a high mechanical performance at high temperatures
according to the object of the present invention, deformation of
the composite material at high temperatures must not occur. For
this purpose, the heat distortion temperature must be at least
150.degree. C. A resin having a higher heat distortion temperature
is preferred.
In the composite material of the present invention, the amount of
fibers constituting the multi-layer woven fabric as the reinforcer
must be 20 to 70% by weight and the amount of the thermoplastic
resin as the matrix must be 80 to 30% by weight. Namely, if the
amount of the multi-layer woven fabric as the reinforcer is larger
than 70% by weight and the amount of the thermoplastic resin as the
matrix is smaller than 30% by weight, it is difficult to cover the
entire woven fabric with the thermoplastic resin, and even if the
textile fabric is covered, a sufficient rigidity cannot be imparted
to the formed composite material and, therefore, it is impossible
to obtain a sufficiently high compression strength and shear
strength. If the amount of the multi-layer woven fabric is smaller
than 20% by weight and the amount of the thermoplastic resin
exceeds 80% by weight, a composite material can be formed but a
sufficient reinforcing effect cannot be realized by the fibers as
the reinforcer, and a sufficiently high compression strength and
shear strength cannot be obtained. Moreover, this composite
material is liable to be deformed under the application of heat.
Therefore, it is necessary to form a composite material by using
the multi-layer woven fabric and thermoplastic resin in the
above-mentioned amounts. If this requirement is satisfied, a
composite material having a honeycomb structure, which has an
especially excellent mechanical performance, can be obtained.
By dint of the above-mentioned structural features, the composite
material of the present invention has a high tensile strength and
compression strength over a very broad temperature range, and even
under a repeated application of stress, the composite material is
not broken and shows a very high impact resistance.
As the thermoplastic resin used for forming the composite material
of the present invention, there can be mentioned, for example, a)
aromatic polyamide-imides represented by the following formula:
##STR1## b) aromatic polyether-imides represented by the following
general formula: ##STR2## c) aromatic polyesters represented by the
following general formula: ##STR3## d) polyether-sulfones
represented by the following general formula:
3) polyether-ether-ketones represented by the following general
formula: ##STR4## f) poly-p-phenylene sulfides represented by the
following general formula:
and g) poly-p-phenylene oxides represented by the following general
formula:
and in the foregoing general formulae a) through g), Ar.sub.1,
Ar.sub.2 and Ar.sub.3 , which may be the same or different, stand
for a substituted or unsubstituted divalent aromatic residue
represented by ##STR5## in which X is --O--, --SO.sub.2 --,
--CH.sub.2 --or --C(CH.sub.3).sub.2 --.
Among these thermoplastic resins, aromatic polyether-imides,
aromatic polyesters, polyether-sulfones and polyether-ether-ketones
represented by the formulae b) through e) where each of Ar.sub.1,
Ar.sub.2 and Ar.sub.3 stands for a p-phenylene group are especially
preferred for the production of the composite material of the
present invention because they are thermoplastic polymers having a
high distortion temperature and being melt-moldable. In the
composite material of the present invention, the above-mentioned
multi-layer woven fabric of the present invention is used as the
reinforcer, and in order to sufficiently utilize the mechanical
characteristics of the constituent fibers of the multi-layer woven
fabric, which is integrally constructed, it is preferable to use a
resin having a relatively high elongation as the matrix resin. Also
from this viewpoint, the abovementioned polymers are especially
preferably used for the production of the composite material of the
present invention.
For the composite material of the present invention, the
above-mentioned polymers can be used singly or in the form of
mixtures of two or more thereof. If desired, a method may be
adopted in which a composite material is once formed by using one
polymer and the composite material is then treated with another
polymer to form a composite material having a plurality of resin
layers.
Preferably, the apparent density of the composite material of the
present invention is 0.03 to 0.2 g/cm.sup.3. The density differs
according to the cell size of the expanded multi-layer woven
fabric, the expansion degree, and the amount of the matrix resin.
If the apparent density is lower than 0.03 g/cm.sup.3, a
sufficiently high compression strength is difficult to attain, and
if the cell size is large in this case, the impact resistance is
degraded. On the other hand, where the apparent density is higher
than 0.2 g/cm.sup.3, the mechanical characteristics of the
composite material can be sufficiently increased, but the
weight-reducing effect is reduced. For these reasons, preferably
the apparent density of the composite material of the present
invention is 0.03 to 0.2 g/cm.sup.3, especially 0.03 to 0.18
g/cm.sup.3, particularly especially 0.04 to 0.15 g/cm.sup.3.
In the present invention, if the above-mentioned preferred
multi-layer woven fabric is used, especially excellent effects can
be attained in the formed composite material. For example, a
composite material in which warps constituting the multi-layer
woven fabric are composed of aromatic polyamide fibers and/or
polybenzoxazole or polybenzothiazole fibers having a tensile
strength of at least 18 g/d and an initial modulus of at least 300
g/d, wefts are composed of carbon fibers or glass fibers and the
matrix resin is at least one member selected from the group
consisting of the above-mentioned polyether-sulfones d),
polyether-ether-ketones e) and aromatic polyamide-imides b) has an
excellent mechanical performance and heat resistance performance
and is very valuable as a structural composite material.
The process for the preparation of the composite material of the
present invention is not particularly critical, and any means
customarily adopted for the production of composite materials can
be adopted. For example, a method can be adopted in which the
expanded multi-layer textile fabric is immersed in the expanded
state in a resin solution to sufficiently impregnate the woven
fabric with the resin, the woven fabric is taken out from the
immersion bath, the solvent is removed by evaporation or extraction
with another solvent, and the formed composite material is washed
and dried; a method in which the expanded multi-layer woven fabric
is immersed in a melt of the resin; and a method in which the
expanded multi-layer woven fabric is coated with a resin liquid by
a brush or the like.
Additives such as an ultraviolet absorber, an antioxidant, a
photostabilizer, and a water repellent can be incorporated into the
composite material of the present invention, in so far as the
intended object of the present invention is attained.
The present invention will now be described in detail with
reference to the following examples. In the examples, all of "%"
are by weight unless otherwise indicated, and the characteristics
of the multi-layer woven fabric and composite material of the
present invention were determined according to the following
methods.
Cell size:
The multi-layer textile fabric was expanded so that the cells had
an equilateral tetragonal or hexagonal shape, and the length
between the confronting layer walls in each cell was measured as
the cell size.
Mechanical performance of composite material:
The compression strength, compression elastic modulus, shear
strength, and shear elastic modulus were measured according to
MIL-STD-401B.
EXAMPLES 1 THROUGH 24
Multi-layer woven fabrics comprising structural units shown in FIG.
3 was formed by using a rapier loom provided with 32 dobbies.
In the structural unit shown in FIG. 3, each of woven fabric layers
11, 12, 13, and 14 having a plain weave texture had continuous
combined portions in parts A and C for every four parts B. In part
A, warps of the second and third woven fabric layers 12 and 13 were
interlaced with three continuously inserted combining wefts 30a,
30b, and 30c through plain weave textures to form a middle combined
portion. This combined portion formed an independent single woven
fabric layer. Accordingly, part A had a three-layer structure
comprising the first woven fabric layer 11, the middle combined
portion layer and the fourth woven fabric layer 14. In part C,
warps of the first and second woven fabric layers 11 and 12 were
interlaced with three continuously inserted combining wefts 31a,
31b and 31c through plain weave textures to form an upper combined
portion, and warps of the third and fourth woven fabric layers 13
and 14 were interlaced with three continuously inserted combining
wefts 32a, 32b and 32c through plain weave textures to form a lower
combined portion. Accordingly, in part C, a two-layer structure was
formed by the upper and lower combined portions. If the
so-constructed multi-layer woven fabric was developed, a
three-dimensional woven fabric having a honeycomb structure was
obtained.
With respect to each of the so-obtained multi-layer woven fabrics,
the kinds of fibers used, the weave densities, and other
characteristics are shown in Table 1.
As shown in Table 1, in Examples 1 through 4 according to the
present invention, aramid multi-filament yarns of 380 d (Kevlar
49.T-968, Du Pont) were used as the warps, and 6,500 warps were
arranged through 32 healds so that the warp density was 325 warps
per inch and 16 layers were formed. As the wefts were used the same
aramid multi-filament yarns of 380 d as the warps in Examples 1 and
2, glass filament yarns 68Tex (filament diameter of 9 .mu.m, E
type, Nippon Fiber Glass) in Example 3, and aramid multi-filament
yarns of 1,140 d (Kevlar 49.T-968, Du Pont) in Example 4. The warp
feed rate was adjusted so that the weft density was 325 or 244
wefts per inch, and the wefts were inserted while winding was
intermittently stopped synchronously with the movement of the weave
texture. In this manner, the weaving operation was carried out.
In Example 5, aramid multi-filament yarns of 380 d were used as the
warps and yarns of 3,000 carbon fiber filaments (Asahi Nippon
Carbon) were used as the wefts, and the weaving operation was
carried out in the same manner as described above.
In Examples 6 through 24, multi-layer woven fabrics shown in Table
1 were formed wherein aramid multi-filament yarns (Kevlar 49.T-968,
Du Pont) were used as the warps, and the same aramid multi-filament
yarns as the warps, glass filament yarns (Nippon Fiber Glass) or
carbon fiber yarns (Asahi Nippon Carbon) were used as the
wefts.
In each of the multi-layer woven fabrics prepared in these
examples, the cell shape was stable and each multi-layer woven
fabric had a honeycomb structure having hexagonal cells, and when
the woven fabric was expanded, equilateral hexagonal cells were
formed. For comparison, when a similar multi-layer woven fabric
composed of nylon 66 multi-filament yarns (see Comparative Example
1) was expanded, although cells of the peripheral portion held for
the expansion had an equilateral hexagonal shape, cells of the
interior portion were distorted. If the expanding force was
increased so as to correct this distortion, the shapes of cells of
the peripheral portion were deformed. Thus, it was confirmed that
it was very difficult to perform the expansion so that uniform
regular cell shapes were formed. Namely, it was confirmed that the
multi-layer woven fabric of the present invention had an excellent
stability and uniformity of the cell shapes. It is estimated that
this effect is due to a high initial modulus of the fibers
constituting the woven fabric.
COMPARATIVE EXAMPLE 1
By using nylon 66 multi-filament yarns of 1,260 d (Asahi Kasei
Kogyo) (initial modulus of 48 g/d) as the warps and wefts, a
12-layer woven fabric having a warp density of 305 warps per inch,
a weft density of 183 wefts per inch and a hexagonal cell size of
1/2 inch was prepared in the same manner as in Example 4. The
characteristics of the multi-layer woven fabric are shown in Table
1. When the woven fabric was expanded, it was found that the
uniformity and stability of the cell shapes of the woven fabric was
inferior to those obtained in Examples 1 through 24.
TABLE 1
__________________________________________________________________________
Warp Weft Thick- density density Cell ness of Example (yarns (yarns
size fabric Weight No. Warps.sup.1 Wefts.sup.1 per inch) per inch)
Texture (inch) (mm) (g/m.sup.2)
__________________________________________________________________________
1 AF380 AF380 325 325 Hexagonal, 16 layers 1/8 25.8 1555 2 AF380
AF380 325 325 " 1/4 51.2 1555 3 AF380 EGF68.sup.Tex 325 325 " 1/4
51.2 1964 4 AF380 AF1140 325 244 " 1/8 26.0 2234 5 AF380
CF1000.sup.fit 122 122 Hexagonal, 12 layers 1/4 38.6 1020 6 AF1140
AF1140 325 183 Hexagonal, 16 layers 1/4 51.2 2987 7 AF1140 AF1140
214 183 Hexagonal, 12 layers 3/16 29.0 2362 8 AF1140 CF3000.sup.fit
214 152 " 1/4 38.6 2636 9 AF1420 AF1420 91 76 Hexagonal, 6 layers
3/4 57.5 1499 10 AF1420 AF1420 122 107 " 3/4 57.5 1909 11 AF1420
CF3000.sup.fit 122 212 Hexagonal, 12 layers 5/8 95.6 2993 12 AF1420
AF1420 427 122 " 1/2 38.6 4894 13 AF1420 AF1420 305 244 " 3/4 57.5
4905 14 AF1420 AF1420 305 183 " 1/2 38.6 4357 15 AF1420 AF1420 305
122 " 1/2 38.6 3809 16 AF1420 AF1420 122 305 " 1/4 38.6 3825 17
AF1420 EGF135.sup.Tex 122 212 " 1/4 38.6 2629 18 AF1420 AF1420 305
152 Hexagonal, 6 layers 3/8 29.0 4083 19 AF1420 AF1420 366 122 "
3/8 29 4352 20 AF1420 Si200.sup.Tex 91 107 " 1/2 38.6 1965 21
AF1420 AF1420 91 91 " 1/2 38.6 1635 22 AF1420 CF3000.sup.fit 91 91
" 1/2 38.6 1639 23 AF195 AF195 325 325 Hexangonal, 16 layers 1/8
25.8 776 24 AF195 CF1000.sup.fit 325 325 " 1/8 25.8 1360
Comparative N66 N66 305 183 Hexagonal, 12 layers 1/2 37.9 3866
Example 1 1260 1260
__________________________________________________________________________
Apparent specific Evaluation.sup.2 Example gravity Cell Weaving No.
K.sub.W K.sub.F K.sub.W + K.sub.F (g/cm.sup.3) shape property
__________________________________________________________________________
1 5398 5398 10796 0.060 A A 2 5398 5398 10796 0.030 A A 3 5398 5045
10443 0.038 A A 4 5398 6408 11806 0.086 A A 5 2026 1711 2737 0.026
C A 6 8535 4806 13341 0.058 A A 7 5620 4806 10426 0.081 A A 8 5620
4450 10070 0.068 A A 9 2926 2444 5370 0.026 B A 10 3924 3441 7365
0.033 A A 11 3924 6207 10131 0.031 A A 12 13733 3924 17657 0.127 A
C 13 9810 7848 17658 0.085 A C 14 9810 5886 15696 0.113 A B 15 9810
3924 13734 0.099 A A 16 3924 9810 13734 0.099 A A 17 3924 4637 8561
0.068 A A 18 9810 4889 14699 0.141 A B 19 11772 3924 15696 0.150 A
C 20 2926 2993 5919 0.051 A A 21 2786 2926 5712 0.042 A A 22 2786
2664 5450 0.042 A A 23 3817 3817 7634 0.030 A A 24 3817 2993 6810
0.035 A A Comparative 10009 6005 16014 0.100 C B Example 1
__________________________________________________________________________
Note .sup.1 AF: aramid multifilament yarn (Kevlar 49.T 968) (the
numerical value indicates the yarn denier) EGF: glass filament yarn
(Nippon Fiber Glass) (the numerical value indicates the yarn
denier) CF: carbon fiber (Asahi Nippon Carbon) (the numerical value
indicates the filament number of the yarn) Si: silicaalumina fiber
N66: Nylon 66 multifilament yarn (Asahi Kasei Kogyo) (the numerical
value
indicates the yarn denier) .sup.2 Cell shape A: excellent, B: good,
C: fair Weaving property A: excellent, B: good, C: fair
Example 25
This example illustrates the composite material of the present
invention.
The multi-layer woven fabric composed of aramid multi-filament
yarns as the warps and wefts and having hexagonal cells having a
cell size of 1/2 inch, which was obtained in Example 14 and had a
width of 700 mm and a length of 1,500 mm, was used.
Stainless steel rods were inserted into cells of the peripheral
portion of the multi-layer woven fabric, and the woven fabric was
expanded by pulling the stainless steel rods so that cells having
an equilateral hexagonal shape were formed. The woven fabric in the
expanded state was immersed in a solution containing 40% of
polyether-sulfone (Victrex 4100P Sumitomo Kagaku) in
N-methyl-2-pyrrolidone. In order to impregnate the fabric
sufficiently with the resin, the immersing bath was sealed and
evacuated by a vacuum pump so that the pressure was lower than 10
Torr. The immersing solution was maintained at room temperature.
The impregnation treatment was thus conducted for about 2 hours,
and the imprenated multi-layer woven fabric in the expanded state
was taken out from the immersing bath and the dripping liquid was
removed. Then, the woven fabric was placed in a hot air drying
furnace at 150.degree. C. for 3 hours to remove the solvent by
evaporation. The temperature in the furnace was elevated to
180.degree. C. and evaporation drying was carried out for 2 hours.
The formed composite material solidified with evaporation of the
solvent was taken out from the furnace. The composite material was
cooled and cut by a diamond band-saw to obtain a composite material
having a width of 600 mm, a length of 1,200 mm, and a thickness of
39.5 mm.
The obtained composite material comprised 55% of the fiber and 45%
of the polyether-sulfone. The physical properties are shown in
Table 2. It was confirmed that the obtained composite material was
superior to the conventional honeycomb structural material shown in
Table 2 in compression and shear characteristics.
COMPARATIVE EXAMPLE 2
A honeycomb multi-layer structure was prepared by treating the
multi-layer structure woven fabric of nylon 66 multi-filament yarns
obtained in Comparative Example 1 in the same manner as described
in Example 25. Cells in the peripheral portion of the obtained
composite material had an equilateral hexagonal shape, but cells in
the inner portion had a distorted ellipsoidal shape. The mechanical
performances of the obtained composite material are shown in Table
2. The composite material was inferior to the composite material of
the present invention in all properties.
EXAMPLE 26
A composite material was prepared in the same manner as described
in Example 25 except that the amount of the polyether-sulfone was
changed. The amount of the polyether-sulfone was adjusted by
changing the concentration of the polyether-sulfone dissolved in
N-methyl-2-pyrrolidone. Other conditions were the same as in
Example 25. The physical properties of the obtained composite
material are shown in Table 2.
From the results shown in Table 2, it was confirmed that if the
amount of the polyether-sulfone as the matrix was smaller than 30%
by weight, satisfactory mechanical properties could not be
obtained.
TABLE 2
__________________________________________________________________________
Composition of composite material (% by weight) Performance of
composite material Multi- Compression Shear Shear elastic layer
Apparent Compression elastic strength in modulus in woven
Polyether- density strength modulus L direction L direction Example
No. fabric sulfone (g/cm.sup.3) (kg/cm.sup.2) (kg/cm.sup.2)
(kg/cm.sup.2) (kg/cm.sup.2) Remarks
__________________________________________________________________________
25 55 45 0.092 46.5 3230 31.5 2040 26 25 75 0.131 60.8 4430 38.4
3150 40 60 0.108 54.1 3750 34.6 2640 65 35 0.083 42.4 2650 21.8
1840 80 20 0.072 18.5 820 8.7 671 Outside scope of present
invention Comparative 55 45 0.081 22.0 670 12.4 840 Example 2
(reference) HRH-10-3/16-4.0* 0.064 39.4 1970 17.2 650
__________________________________________________________________________
Note *(NOMEX .RTM. Honeycomb supplied by Showa Hikoki Kogyo)
EXAMPLE 27
A multi-layer woven fabric and a composite material were prepared
in the same manner as described in Example 25 except that a
polyether-imide resin (Ultem 1000, General Electric) was used
instead of the polyethersulfone used in Example 25.
The characteristics of the obtained composite material were as
shown below.
Multi-layer woven fabric (% by weight)/polyetherimide resin (% by
weight)=60/40
Apparent density=0.092
Compression strength (kg/cm.sup.2)/compression elastic modulus
(kg/cm.sup.2)=54.9/3,200
Shear strength (kg/cm.sup.2) in L direction/shear elastic modulus
(kg/cm.sup.2) in L direction=32/3,510
Shear strength (kg/cm.sup.2) in W direction/shear elastic modulus
(kg/cm.sup.2) in W direction =24.5/2,860
EXAMPLE 28
By using multi-filament yarns of 400 d, composed of
polybenzoxazole, as the warps and wefts, a multi-layer woven fabric
was prepared by arranging 324 warps through healds as in Example 1
so that the warp density was yarns per inch and an 8-layer
structure was formed and inserting wefts as in Example 1 so that
the weft density was 325 yarns per inch. The obtained multilayer
woven fabric had hexagonal cells having a cell size of 1/8 inch,
and the thickness of the woven fabric in the expanded state was
12.9 mm.
The multi-layer woven fabric was treated in the same manner as
described in Example 25 to obtain a composite material comprising
50% of the polyethersulfone. The characteristic values of the
obtained composite material were as shown below, and it was
confirmed that the composite material and excellent
performances.
Apparent density=0.089
Compression strength (kg/cm.sup.2)/compression elastic modulus
(kg/cm.sup.2)=62.5/4,650
Shear strength (kg/cm.sup.2) in L direction/shear elastic modulus
(kg/cm.sup.2) in L direction=37/3,930
Shear strength (kg/cm.sup.2) in W direction/shear elastic modulus
(kg/cm.sup.2) in W direction=27/3,050
When the multi-layer woven fabric of the present invention having
the above-mentioned structure is extended, there is formed a
honeycomb structure, and this multi-layer woven fabric is
characterized in that the respective woven fabric layers are
integrated by interlacing warps or wefts of adjacent woven fabric
layers with common wefts or warps. Therefore, interlaminar
separation is not caused, and even though a high weight-decreasing
effect is attained, the tensile strength and shear strength between
adjacent layers are very high. Moreover, the structure is stable
and the heat resistance is excellent. Accordingly, the multilayer
woven fabric of the present invention is very suitable as a
reinforcing woven fabric for the production of a composite material
having such excellent characteristics.
The composite material of the present invention comprising this
multi-layer woven fabric and a specific resin has a light weight
and shows a high tensile strength and compression strength over a
broad temperature range, and even if stress is imposed repeatedly
on the composite material, the composite material is not broken,
and the impact resistance is very high. By dint of these
characteristic features, the composite material of the present
invention is very valuable as a structural material for an
aircraft.
* * * * *